A child car seat is usually provided with a safe belt for safely protecting the child seating on it, and the safe belt is required to be clamped and positioned during actual use. The existing child car seats are generally provided with a pushbutton type of positioning block on the base seat. By pressing the positioning block, the positioning block coordinates with the base seat to clamp the safe belt. A installing groove is required to provide on the base seat to correspond to the positioning block. But in actual use, the safe belt is in a free state before being clamped, that is, the safe belt is apt to shift with respect to the installing groove, therefore, the safe belt is not easy to be stuck in the installing groove when pressing the positioning block. Moreover, even though the safe belt and the installing groove are aligned manually before pressing the positioning block, there are still other problems, that is, a great press force is needed to press the sate belt tight, and the positioning block has a hidden risk to come out from the installing groove, affecting the actual property of the safe belt.